A policeman is among the victims when the passengers of a late-night bus are machine-gunned. With only one semi- conscious survivor and no other witnesses, the detectives try to learn from the identities of the dead why this happened and who the killer could be. Climax includes excellent chase.

Also Known As (AKA): San Francisco ciudad desnuda, Le flic ricanant, L’ispettore Martin ha teso la trappola, S. Francisco Cidade Nua, Massenmord in San Francisco, An Investigation of a Murder